Experimentally, cerebral ischemic edema can be produced easily in 30% of Mongolian gerbils by unilateral ligation of the common carotid artery. The cerebral water content was assessed by the determination of wet and dy weight and the specific gravity of the tissues. In short-term ischemia of 1 hour duration, the cerebral water content was increased, but did not show any progression until 10 houus after the release of arterial occlusion. At this time, the percent of water content was more pronounced coinciding with the increased permeability of blood-brain barrier to Evan's blue tracer. A week later only half of the animals showed recovery. In long-term ischemia, progressive accumulation of water content was observed with prolonged duration of ischemia.